The present invention is an improvement upon the pallet conveying system shown in U.S. Pat. No. 4,532,869. Conventional pallets of this type have a drawback that it is not easy to change the sizes or the structures thereof and the manufacturing costs are high because, as seen in U.S. Pat. No. 4,532,869, they are fabricated from a machined one-piece element of plate-like material, or from an aluminum casting, or the like. Thus, it has been difficult to obtain most suitable pallets at reasonable prices.
Furthermore, as seen in the same U.S. patent, in order to stop the pallet upon the collision from behind, it has been conventional to use a stop lever projecting from the front end of the pallet having an actuator to move the lever so that it may cause the driven roller to gyrate or turn its roller axis when such a collision occurs. In order to stop the pallet in response to a separate limit stop, it has been conventional to provide a cam which may rotate upon abutment with the limit stop such that the rotation of the cam causes gyration of the driven roller, as seen in FIGS. 4 and 5 of said patent. Therefore, such a conventional apparatus has a drawback that it is structurally complicated and comprises many component parts.
It is possible to stop the pallet by letting the above-mentioned projecting stop lever abut against the separate limit stop; however, in such a case, since the forwardly projecting stop lever actuator must be in a position to abut the preceding pallet from behind, the separate limit stop is required to project upright at least as high as the stop lever actuator. However, in case of storing a number of pallets, each pallet is provided with an abutment for storage which is caused to abut against the actuator on the lever, and consequently, should the separate limit stop project so that it may contact the said actuator, it will inevitably collide against the abutment provided for the above-mentioned storage. Therefore, the separate limit stop must be manipulated into the path of travel of the actuator after detecting the passage of the preceding pallet and within the time period until the next pallet arrives, which is cumbersome, and in the case where a plurality of pallets are in series contact with each other, such a separate limit stop may not be used to stop any of the intermediate pallets of the series.
The object of this invention is to provide a pallet in which the above-mentioned problems have been solved.